Add error states to remaining form elements
- FormGroup: adjusted labels to be children elements, versus
sub-components
- Textarea: removed icon groups
- Textarea: added missing noResize flag
- Toggle: removed .tw-toggle__label-on, .tw-toggle__label-off classes (e91d307)
refactor FormGroup element structure
- label & hint are children elements of FormGroup until further notice
- added missing optional flag for labels (6e797d0)